Scarecrow

The Scarecrows are a species of lesser demons that appear in Devil May Cry 4. Each type of Scarecrow is a a burlap sack filled with Trypoxylus beetles, and though these insects possess no individual will, the are able to act as one to animate the demon. They are very similar to the Marionettes in Devil May Cry, and serve as basic enemies. There exists three versions of Scarecrows.

Scarecrow (Leg) and Scarecrow (Arm)
The Scarecrow serves as the basic enemy of Devil May Cry 4. Scarecrows have executioner's blades fitted to their body, and are differentiated by its position — Scarecrow (Arm)'s have blades on their arms and fight with simple patterns that are easy to avoid, while Scarecrow (Leg)'s have bladed legs which allow them to perform intricate, acrobatic feats of violence on their victims.

Mega Scarecrow
The Mega Scarecrow is a Scarecrow that is filled to the brim with Trypoxylus beetles and has several blades on its arms, legs, and back. It is stronger than its smaller brethren and is able to perform vicious spinning attacks, but it is slow and can easily be kept from responding to the player's attacks. When it dies, the blade on its back will fly off and then fall on its remains, much like the Sins, and this blade can still damage the player.

Background
Trypoxylus is the genus to which Japanese rhinoceros beetles belong. These beetles are frequently depicted as a cartoon character in popular media, much as bears or lions are in the United States.

Trivia

 * After defeating the final boss, the player can unlock the epilogue cutscenes by defending Kyrie from a mob of Scarecrow (Arm) and Scarecrow (Leg)'s for 1:30 minutes.
 * In the small scene that shows you Scarecrows dancing in the street and on destroyed cars there are different looking Scarecrows from the ones you fight. One of them has a different head design and its head is colored yellow and purple. The other one is a Scarecrow (Arm) that has the head and mask of a Scarecrow (Leg). It's head is also colored differently. These appear to be Scarecrows from early 2006 as they appeared in TGS 2006 gameplay videos as fightable. It is likely Capcom abandoned this Scarecrow design (for fighting).